Problem saving cloned EF entity to DB

Question

I have managed to successfully clone an EF entity using serialization and deserialization. If I set the EntityKey to nothing, I can add it to the context. But when I try to SaveChanges, I get an error saying that the primary key must be unique. This makes sense since the clone has the same key. So I need to change it beforehand.

But the primary key is autoassigned by the DB (SQLite) upon insertion, and since the PK is not nullable I cannot set NewEntity.ID=Nothing, which I presume would tell the context that this entity should receive a temporary key until it is inserted.

If I set NewEntity.ID = 30804328 or some arbitrary (unused) number, it will save to DB fine. But I am very unkeen to query for an unused ID value every time I want to clone an entity.

I understood that the context would treat a detached entity as new when it was 'AddObject'ed, and assign it a temporary key so the DB could do the assignment and then the context would receive the updates. Is this not the case?

How do I resolve this? Thanks for any advice!

score 3 · Answer 1 · edited May 23 '17 at 12:31

3

This is also covered here: Cloning data on Entity Framework

If looks like the following code is the way to go:

  context.Detach(entity);      
  entityCollection.Add(entity);
  context.SaveChanges(); // New id will be assigned here

edited May 23 '17 at 12:31

Community

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answered Feb 26 '11 at 11:46

Shiraz Bhaiji

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Thanks for the reply. I tried both the serialization method and the other code provided in the link. My problem is not with the cloning process, nor calling AddObject; it's the insertion into the database. The context is not assigning an interim key, it is retaining the original and they clash upon insertion. I cannot set the key to Nothing because the PK is not nullable. – TripleAntigen Feb 27 '11 at 02:40

score 1 · Accepted Answer · answered Aug 25 '11 at 16:38

I FOUND THE SOLUTION FINALLY. The problem was that the table involved had a primary key identity but Autoincrement was not set. It appears that though the ID key is zero by default when creating a new entity, and it cannot be changed by assignment, it is auto-assigned in the case that Autoincrement is set. But clearly this cannot be resolved automatically if autoincrement (or computed) is not set.

Problem saving cloned EF entity to DB

2 Answers2